In order to deliver value added services such as video on demand and internet access as well as to provide more efficient use of the available RF spectrum, modem cable TV networks have moved from a primarily analog system to one which is largely digital, at least for large portions of the available RF spectrum. Of course, at the delivery end traditional cable TV networks are comprised of a distribution network based on 75 ohm coaxial cable. Such networks support a bandwidth of up to about 1 GHz. However, in order to take advantage of this bandwidth, both analog TV broadcasts and digital signals are modulated prior to transmission to particular predefined frequency bands, thereby ensuring that mutual interference is kept to a minimum.
The above prior art systems suffer from many drawbacks. For example, interconnections between sources of analog and digital signals are typically hardwired to the modulators meaning that reconfiguration is difficult, typically requiring a technician to manually reconfigure the system. For conventional broadcast TV this is generally not a problem as the channel line up is predefined. On the other hand, for Video on Demand (VOD) systems, where the stream of video data flows between the delivery system and set top box in a manner which is largely transparent to the user such hardwired systems are unable to allow for efficient use of the available bandwidth, in particular as the potential for switching video streams from one frequency band to another is limited if not impossible.